This invention relates to latch and lock mechanisms for movable doors in general, and sliding doors in particular. The invention was designed with slidable overhead garage doors in mind.
Many prior art garage doors are equipped with a lock which has a handle. Rotation of the handle controls latching or locking devices located at the sides of the doors via lock bars. It is also well known that many of these prior art locking devices are equipped with spring loaded latch catches and similar devices, so that the handle and lock can be placed in their closed position while the door is still opened. Upon the actual closing of the door, the side mounted latch catches are released, thus securing the door.
Many prior art doors, particularly those which are used to close large openings, have a great deal of play between the door and the tracks or rails upon which they slide. Such play has, in part, been necessary and, in part, been the result of a desire to keep the cost of such doors low. This has been especially true with respect to slidable overhead garage doors. Of course, the movable metal rods and the stationary members which receive the rods, and which make up the latch mechanisms, are also subject to such play. The play permits the door panel to be moved a certain extent if a force of an appropriate intensity is applied to the door, as during an attempted break-in. Sideway movement creates the risk of the side mounted latch mechanism becoming ineffective and, in fact, unlocked, even when the door mounted lock itself is in the locked position. Extreme shifting movement of the door can be achieved through a rythmic application of force, resulting in a resonant build-up of movement of the door panel. Even if the side mounted latch mechanism can structurally withstand such forces, the forces may cause the operative latch member to move, thus permitting the door to be opened.